Propane deresinating



Jan. 17, 1939. P. c. KEITH. lR., ET AL 2,143,882

PROPANE DERESINATING Filed Aug. 15, 1955 2 Sheets-Sheet l I LUBE Jroc PROPANE 370M615 $702 405 M 7 SETTLE/2 rand. Liv .5/0/7 .7 46 w? Jan. 17, 1939. P. c. KEITH JR, ET AL 2,143,882

PROPANE DERESINATING Filed Aug. 15, 1935 2 Sheets-Sheet 2 LUBE sroc 11 sromss pQOpA/VE I STORAGE fispha/f L/gh Blend/n9 Cy/mder Res/n5 lower layer Sfcck lower propane upper /a yer upper layer layer insc/ ub/e propane so lub/e propane so/ub/e propane insoluble 19 2 115 venjfors- Percy C. Kat/1J1.

Bohemia. WL' b.5012 Myra'nJL' gJiO/L Patented Jan. 17, .1939

PROPANE DERESINATING Percy 0. Keith, Jr., Peapack, N. J., Robert E. Wilson, Chicago, Ill., and Myran J. Livingston, Mariners Harbor, Staten Island, N. Y., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application August 15, 1935, Serial No. 36,280

15 Claims.

This invention relates to the refining of lubricating oils with propane and it pertains more particularly to the separation of resins from a substantially asphalt-free lubricating oil stock.

An object of the invention is to produce maximum yields of high quality lubricating oils from stocks which are substantially free from asphalt, but which are characterized by a tendency to form carbon, and which have heretofore required expensive clay treatments for obtaining the desired color and stability against oxidation and sludging.

A further object is to increase the amount of neutrals and/or light blending oils obtainable 15 from Pennsylvania crudes and from residual stocks which contain objectionable resins or potential sludging and carbon-forming components.

A further object is to provide an improved propane fractionation process which will simplify Q procedural steps and decrease refining costs, particularly the cost of clay treating-which is by far the most costly operation in the refining of Pennsylvania type oils. This object, stated somewhat difierently, is to remove by simple and inexpensive means a large proportion of the color-bearing material which has heretofore been removed by clay, so that the cost of claying may be reduced about 400 to 600%.

A further object is to establish the optimum 1 sequence of steps and the optimum operating conditions in each step for refining lubricating oil stocks with propane. Other objects will be apparent as the detailed description of our invention proceeds.

We have discovered that there is a class of high molecular weight hydrocarbons in residual lubricating oil stocks which are not asphalts but which nevertheless are objectionable because of their color and because of their tendency to form sludge and to deposit carbon; these objectionable compounds may be termed resins.

We have found that these resins are not separated from oils in ordinary propane deasphalting processes and we have also found that they are 2; present in oil stocks of the Pennsylvania type. They can not economically be removed from the oil by distillation. We have discovered, however, that if the lubricating oil stock is separated into light and heavy fractions by treatment with propane at high temperatures, these resins are concentrated in the heavy fractions. We have found that by giving these heavy fractions which contain the resins a low temperature treatment with additional propane, the resins may be sep- 55 arated from the heavy oils. These resins are valuable for special uses, and the oil from which they are separated is a very high quality cylinder stock.

With the use of our invention, the Pennsylvania refineries can radically change the ratio of bright stocks to neutrals. At present a Pennsylvania refiner normally reduces to 20% bottoms when producing a bright stock having a Saybolt viscosity of 150 seconds at 210 F. If our invention be employed the bottoms can be reduced to a product having a viscosity of approximately 190 seconds at 210 F., and representing about 15% on the crude. The 5% overhead gained by this further reduction can be processed to neutrals. The 190 seconds viscosity bottoms can then be propane deasphalted with a loss of roughly 1% (based on crude) to produce a finished bright stock of 150 seconds Saybolt at 210 F., and with a very large saving in filtering cost.

Alternatively, a Pennsylvania refiner may fractionate a 20% residuum into about 16% of an excellent blending stock having a viscosity at 210 F. of 125 seconds Saybolt, and we may obtain about 2% of resins and 2% of a high quality cylinder stock of about 284 seconds Saybolt viscosity at 210 F. Thus we may either markedly increase the amount of neutrals obtainable from Pennsylvania crude, or we may produce a large quantity of a high grade blending oil of lower viscosity than ordinary bright stock, and at the same time we may produce the necessary high quality cylinder stock, and a resin fraction.

. Our invention is also applicable to Mid-Continent and other crudes wherein a residuum stock has had a preliminary deasphalting treatment. Also, the flash, stability against sludging, and viscosity characteristics of lubricating oils from mixed base crudes can be materially improved by taking a longer cut of distillate lubricating oils, preferably running Mid-Continent crude to about to bottoms. The resulting heavy residuum maybe deasphaltcd and deresinated in accordance with our invention, and the oil from these treatments may be blended with the heavy distillates to obtain maximum yields of high quality lubricating oil with excellent flash viscosity and excellent stability against sludging.

In practicing our invention we first obtain a substantially asphalt-free lubricating oil stock of high molecular weight; this may be a Pennsylvania residual oil, a very heavy distillate such as overhead bright stock, or a deasphaltcd residuum from mixed base crudes. Next we mix this stock with about 4 to 10 volumes of propane and alobi low the mixture to separate into two phases at a temperature of about 160 to 190 F. The propane soluble fraction is an excellent blending stock of relatively low viscosity, ood color and good stability against sludging. In some cases it is desirable to follow up this high temperature fractionation with a washing step to insure the removal of low viscosity oils from the remaining mixture of cylinder stock and resins. Finally, we separate the resins from the cylinder stock by low temperature propane separation, a step which would be impossible in the presence of the oil removed at the high temperature.

Our invention will be more clearly understood from the following description and from the accompanying drawings which form a part of the specification, and in which,

Fig. 1 is .a diagrammatic elevational plan of an improved system for treating Pennsylvania residuums, and

Fig. 2 is a diagrammatic elevational plan of a system which is also suitable for treating Mid- Continent or other mixed base crudes.

Before describing our invention in detail it should be understood that the propane referred to herein is preferably relatively pure but that it may be mixed with considerable quantities of butane, isobutane and/or ethane. The principles of our invention may be utilized with ethane, isobutane or butane instead of propane by making the necessary adjustments of temperature, pressure and proportions used. Although propane is used in our preferred embodiments, it should be understood that our invention is applicable to other normally gaseous hydrocarbons.

As an example of refining of Pennsylvania residuum, we may start with a 21% residuum having an A. P. I. gravity of 25.7, a flash of 565 F., a viscosity of 161 seconds Saybolt at 210 F., a pour test of 45 and a Conradson carbon of 2.6%. One volume of this stock is pumped from storage tank H] by means of pump II through line l2 to mixing tank l3, wherein it is intimately mixed with 6 volumes of liquid propane from storage tank l4, line I5 and pump 16. An orifice mixer or a mechanical mixer may be used and a suitable heat exchange may be provided so that the mixture is discharged at about 160 F., into horizontal settling tank 11, which is necessarily designed to withstand high pressures, preferably up to about 600 pounds per square inch.

In tank l1 about 72% of the low viscosity lighter colored oil with practically all of the propane will be separated from 28% of heavier oils and resins, the propane light oil fraction being withdrawn through line i8 and the heavy oil fraction through line l9, preferably through liquid level controlled valve 20, into a second mixer 2 I. Additional propane from line I5 is introduced into mixer 2| b'y pump 22 and the temperature of the mixer is so regulated that it may be introduced into settling tank 23 at about 130 F. About two volumes of propane (based on oil stock charged to the system) may be introduced at this point so that the mixture entering settling tank 23 contains about 7 volumes of propane per volume of oil. In this step we wash out about 6% (based on original stock) of the lower viscosity lighter colored oil and withdraw it through line 24 for combination with oil in line l8, or through line 25 for separate recovery.

The phase separation in tank 23 gives 22% of a mixture of heavy oil and resins which are withdrawn from the base of this settler through line 26 in amounts regulated by liquid level control valve 21. This oil is introduced into mixer 28 wherein it is intimately mixed with about two more volumes of additional propane (based on original stock) from line l5 and pump 29. The

temperature of this mixture is regulated so that it will be discharged into settling tank 30 at about 100 degrees F.,-about 9 volumes of propane to one volume of oil.

In settling tank 30 an upper propane soluble fraction is withdrawn through line 3! to still 32 which is heated by still coil 33, propane being removed through lines 34 and 35 and condenser 36 to propane storage tank I l. The finished oil withdrawn from the base of still 32 is a cylinder stock or steam refined oil characterized by an A. P. I. gravity of 24.5, a flash of 600 degrees F., a viscosity of 228 seconds Saybolt at 210 F., a pour point of 50 F., a Conradson carbon of 2.5%, a color of 3 D. Tag Robinson, and a Holde asphalt (hexane insoluble) of 0%. This oil constitutes about 17% of the residuum or 3.57% of the crude. Since most of the resins and sludge-forming constituents have been removed by the deresinating step it may be brought to color and stability by a relatively light clay treatment, either hot-contacting or percolation.

Heavy resins are withdrawn from the base of settler 30 through line 38 in amounts regulated by liquid level controlled valve 39. These resins may be freed from propane in still 40 by steam coil 4!, propane being removed through line 42 to propane line 35. The heavy resins withdrawn through line 53 constitute about 5% of the charging stock or about 1.05% of the original crude,- it is a relatively hard resin and has a Conradson carbon of about 20%.

The light lending oil is passed through line 46 to propane line .35. The light oil is withdrawn from the base of still 44 through line 41 and if it has not had a dewaxing or clay treating step it will constitute 78% of the charging stock or 16.38% of the original crude. It will have an A. P. I. gravity of 27.0, a fiash of 550 F., a viscosity of 116 seconds Saybolt at 210 F., a pour point of 90 F., a Conradson carbon of 1.3% and a color of 1% D. Tag Robinson.

This oil may be dewaved and/or clayed while it is still in propane solution or subsequent to the removal of the propane. Thus by closing valve 48 and opening valve 49 the solution may be bypassed to dewaxing system 50 and thence to clay tower 5|. By' properly regulating valves 52 to 56 we may pass the oil through the dewaxing system or the clay system or both. If an acid treatment is employed it should also be carried out in propane solution to avoid emulsion diificulties.

An important feature of our invention is the fact that only about /3 as much clay is required to obtain a given color as would be required on oils which have not been deresinated. If the 21% residuum is clayed to a color of 3.1 D. Tag Robinson, it will require about 39% by weight of contacting clay at a temperature of 500 degrees F. After the resins have been removed, as herein above described, we have found that the same color may be obtained by the use of only 6% by weight of contacting clay. To obtain a color of 1% D. Tag Robinson on the original residuum, 22% contacting clay would be required, while the same color can be obtained after propane dewaxing with less than 2% of the clay. It will thus be seen that enormous savings are afforded in the cost of lubricating oil finishing.

As another exampleof our invention we may treat in the system of Fig. 2 a Pennsylvania rewith 9 volumes of propane from storage tank 14,

line I5 and pump 16. When the mixture is allowed to settle in separator 51 at a temperature .of about 135 to 140 F., a propane insoluble lower layer will separate out, which, when freed from propane, will be found to have an A. P. I.' gravity of 11.5 F., and a Conradson carbon of 12.5%. These materials may be called primary resins and they may amount to 2.2% by volume of the stock charged. 7

The propane soluble oil from settling tank 51 may be withdrawn through line 59 to tank 60 and thence introduced by pump Bl into mixture 62, wherein it may be admixed with additional propane introduced from line l5 by pump 63. Usually, however, the propane already admixed with the oil is sufflcient and it is only necessary to pass the solution through heater 64 to raise its temperature to about 160 F., before introducing it into settler 65. At this'high temperature the cylinder stock will be thrown out of the solution and in it will be concentrated the secondary resins, leaving a yield of about 80% of a light blending oil which, when freed from propane, has an A. P. I. gravity of 265 F., a viscosity of 210 F. of 124 seconds Saybolt, a color of 1 Tag Robinson, a Conradson carbon of 1.6%, a flash of 585 F., and a viscosity gravity constant of .812.

The propane insoluble layer from settler 65 may be withdrawn through line 61 to collar 68, from which it may be forced by pump 69 to mixer 10 wherein it may be intimately mixed with about 1 volumes (based on original charging stock) of propane from line l5 and pump 1 I. This mixture should be at a temperature of about 120 F., and a suitable heat exchanger may, if necessary, be employed between mixer 10 and settling tank 12. In settler 12 there will be a separation of propane soluble cylinder stock from propane insoluble secondary resins. The cylinder stock, when freed from propane, amounts to about 9 or 10% of the charging stock, it has an A. P. I. gravity of 24.2, a viscosity at 210 F. of 284 seconds Saybolt, a color of 2 D. Tag Robinson, a Conradson carbon of 2.7%, a flash of 590 F., and a viscosity gravity constant of .815. The secondary resins amount to about 8 to 9% by volume of stock charged and are characterized by an A. P. I. gravity of 21 F., a Conradson carbon of 6.0%, a viscosity at 210 F. of 757 seconds Saybolt and a viscosity gravity constant of While the above examples have been specific to Pennsylvania residuums, it should be understood that our invention is also applicable to residuums from mixed base crudes, and it will be observed that in employing such crudes settler 5'! may be operated at temperatures of from about to 140 F., for removing asphalt as well as primary resins. Here again it is necessary that the deasphalted oil be fractionated at a relatively high temperature to concentrate the secondary resins in heavy oil in order that these resins may finally be removed from the heavy oil in the subsequent low temperature propane fractionation step.

In preparing bright stock from mixed base crudes such as Mid-Continent, we have found that increased yields and better flash-viscosity relationships are obtained by running to very low bottoms, deasphalting the bottoms in accordance with our invention to give an extremely viscous cylinder stock, and to blend this cylinder stock with a very heavy distillate lubricating oil fraction. Thus, instead of merely distilling to 25% bottoms, deasphalting and finishing, we may take an overhead cut of that fraction between 80% off and off and we may blend with this narrow cut of heavy distillate the cylinder stock prepared from the deasphalting (at relatively high propane ratios) of -10 to 15% bottoms. This method of refining improves the flash-viscosity relationship of the finished oil; it eliminates low boiling fractions heretofore included in bright stocks, and it results in the production of a much higher quality oil than has heretofore been obtained from equivalent reduced crudes.

The blend may, of course, be acid treated and/or clayed to color in accordance with conventional practice, but the removal of resins and color bodies will be found to markedly decrease cost of clay treating.

While we have described our invention in detail, it should be understood that we do not limit ourselves to any of the particular charging stocks or operating conditions hereinabove described. We have already pointed out how Pennsylvania refiners may take an additional 5% of their crude overhead to increase the production of neutrals and how the heavy residuum may be deasphalted and deresinated to yield a bright stock which will increase claying yields from 400 to 600%. Many modifications and alternative forms of our invention will be apparent from the above description to those skilled in the art.

We claim:

1. The method of refining a substantially asphalt-free lubricating oil stock which comprises admixing said stock with about 4 to 10 volumes of propane at a temperature of about 160 to 190 F., separating a propane soluble fraction of relatively low viscosity oil from the propane insoluble fraction of heavier oils and resins, and subsequently separating the resins from the heavier oils in the absence of the lighter oils by admixing the insoluble layer from the first separation step with additional amounts of propane and effecting phase separation at a lower temperature.

2. The method of claim 1 wherein the temperature of separating resins from heavy oils is about to F.

3. The method of refining residual lubricating oil stocks which comprises admixing said stocks with about 4 to 10 volumes of propane and effecting phase separation at a temperature not substantially higher than F., removing the propane soluble layer from this separation step and heating it in admixture with propane to a temperature of at least about F., to cause the separation of heavy lubricating oil fractions from propane soluble lighter lubricating oil fractions and to cause the concentration of the resins in the heavy oil fractions, removing the insoluble mixture of heavy oils and resins, intimately admixing said fraction with additional propane, eifecting phase separation at a temperature not higher than about 120 F., whereby the heavy oil fractions are dissolved by the propane and the resins are precipitated therefrom, separating the resins from the heavy oil solution and removing propane from the resins, the heavy oil fractions and the lighter oil fractions respectively.

4. The method of increasing the yield from substantially asphalt free residual lubricating oil stock of oils suitable for automobile crank case lubrication which method comprises blending said stock with about. 6 to 10 volumes of propane, effecting phase separation of this blend at a temperature of about 160 F., separately removing the propane-soluble phase from the undissolved oil phase, washing said undissolved oil phase with additional amounts of propane, using a higher propane ratio and a lower temperature,

combining the propane-soluble material from the washing step with the first-namedpropane-solw ble material, and depropanizing said propanesoluble material.

5. Themethod of claim 4 which includes the step of dewaxing said oil in propane solution.

6. The method of claim 4 which includes contacting said propane-soluble oil with clay and using /2 to the amount of clay that would be necessary for contacting the residuum before the propane treatment.

'7. The method of claim 4 wherein the propanesoluble oil fraction is first dewaxed and then contacted with clay.

8. The method of claim 4 wherein the undissolved oil is subsequently diluted with additional propane and phase separation is effected at from about room temperature to 130 F., to yield a propane-soluble cylinder stock and a small amount of resins.

9'. The method of fractionating lubricating oils by means of propane which comprises initially separating a propane-soluble from a propaneinsoluble fraction with a propane ratio of about 6:1 to 10:1 at a temperature of about 160 F., mixing the propane-insoluble fraction from the first separation step with additional propane, separating an insoluble phase from the mixture at a lower temperature than was used in the first separation, mixing the second insoluble phase with additional propane, and separating resins from propane-soluble oil at a temperature not higher than about 120 F.

10.-The method of increasing clay yields in the refining of substantially asphalt-free lubricating oil stocks which comprises treating said stocks with propane at high temperatures to concentrate the resins in a small amount of heavy oil, and subsequently treating the heavy oil-resin mixture with propane, using at least a 6:1 propane ratio at lower temperatures to separate the resins from the heavy oils in the absence of light amassa oils, and treating said oils with clay subsequent to the removal of resins. J E

11. The method of refining a substantially asphalt-free lubricating oil stock containing resins of the type that are usually removed from oil by clay, which method comprises concentrating said resins in a heavy fraction of said oil, treating said fraction with about 10 volumes of liquid propane at a temperature below 160 F. but above 100 F. to separate said resins from said fraction, and separately removing propane from said resins and from the deresinated oil -moval of the resins by the propane treatment effecting substantial savings in the finishing treatment.

14. The method of making a bright stock which comprises fractionating a crude petroleum oil to obtain a fraction which is substantially free from light oils, which has a viscosity substantially higher than that of the desired bright stock, and which contains about 1 to 4% of resins of the type which are usually removed by treatment with clay, which method comprises admixing said fraction with about 10 volumes of liquid propane and efiecting phaseseparation of said fraction in said liquid propane at a temperature at which the oil is soluble in the propane but the resins are insoluble therein, separating the oil phase from the resin phase and finishing the oil phase in the absence of the separated resins.

15. The method of claim 14 wherein the finishing step includes a treatment with clay, but wherein the amount of clay is less than onehalf the amount which would be required for treating the fraction before resin removal.

PERCY C. KEITH, JR. ROBERT E. WILSON. MYRAN J. LIVINGSTON. 

